Fluorinated polymers typically comprise repeating units, each unit including a backbone portion attached to a fluoroalkyl side chain. The fluoroalkyl side chain typically includes a hydrocarbon spacer group and a terminal perfluoroalkyl tail. The stable and inert perfluoroalkyl tail is hydrophobic and oleophobic.
Such fluorinated polymers can be mixed with an inert carrier or dissolved in a solvent and applied to a hydrophilic material (for example, paper, cloth, metals, glass, or ceramic) to impart water and oil repellency to the material. The perfluoroalkyl tail portions of the polymer can organize or align at the solid/air interface of the material to create a low energy surface.
Conventional fluoroalkyl side chains generally have the formula CnF2n+1(CH2)m— where n typically ranges from 6 to 12, and m typically ranges from 1 to 11. Adjustment of the number of methylene moieties (—CH2—) in the spacer group, as well as the number of carbon atoms in the CnF2n+1 perfluoroalkyl tail, can result in the organization or alignment of the side chains of the polymers and in the formation of crystalline-like regions when the polymer is applied to a substrate material. It has been postulated that an increase in the number of methylene moieties in the spacer group can compensate for the decrease in the value of n that is now viewed as desirable from an environmental residue perspective.
In synthesizing conventional fluorinated polymers, however, the perfluoroalkyl chain length generally has been the only part of the side chain that has been varied to enhance the formation of crystalline regions (and the accompanying ability to impart low surface energy characteristics). This may have been due to a scarcity of industrially useful methods for preparing side chains of varying polymethylene content.
Compounds comprising polymethylene moieties have been prepared by different synthetic techniques, but each has its own advantages and disadvantages. One such method has been the telomerization of ethylene using various telogens.
Telomerization has been defined as the process of reacting, under polymerization conditions, a molecule YZ (termed a “telogen”) with more than one unit of a polymerizable compound having ethylenic unsaturation (termed a “taxogen”) to form products called “telomers” having the formula Y(A)nZ, wherein (A)n is a divalent radical formed by chemical union, with the formation of new carbon bonds, of n molecules of the taxogen (the unit A being termed a “taxomon,” n being any integer greater than one, and Y and Z being fragments of the telogen attached to the terminal taxomons). Telomerization is distinct from interpolymerization (more commonly referred to as copolymerization), in that in telomerization only one molecule of telogen is incorporated into each resulting telomer molecule, and the average molecular weight of the telomer product is, in general, considerably lower than that of an interpolymer formed under comparable conditions.
Ethylene telomerization produces a mixture or distribution of telomers having varying numbers of methylene moieties. For the telogens selected and the conditions utilized, however, ethylene telomerizations have typically resulted in telomers of only limited chain length. Industrial use of fluoroalkyl or perfluoroalkyl halides, in particular, has typically focused on the incorporation of only one molecule of ethylene (n=1).